1. Field of the Invention
The present invention relates to a blankmask and a photomask using the same, and more particularly, to a blankmask having a hard film formed therein for realizing a pattern having a half-pitch of 32 nm or less, particularly 20 nm or less, and a photomask using the same.
2. Discussion of Related Art
Today, ultrafine processing technology for semiconductors has emerged as a very important factor to meet the need for fine circuit patterns accompanied by high integration of large-scale integrated circuits (ICs). In the case of highly integrated circuits, circuit wires become finer for the purpose of low power consumption and high-speed operations, and there are growing technical demands for contact hole patterns for interlayer connections, circuit arrangement for high integration, etc. Therefore, in the manufacture of the photomask on which an original circuit pattern is recorded, lithography technology capable of forming finer circuit patterns and recording more precise circuit patterns on the photomask is required so as to meet such demands.
Binary blankmasks using a light shielding film, and phase shifting blankmasks using a phase shifting film and a light shielding film are commercially available as raw materials for photomasks manufactured using the lithography technology. Further, blankmasks further including a hard film have been developed in recent years.
In the case of the blankmasks including the hard film among the above-described blankmasks, the structures of binary blankmasks using a molybdenum silicide (MoSi) compound as a light screening film, and the structures of phase shifting blankmasks using a molybdenum silicide (MoSi) compound as a phase shifting film and a chromium (Cr) compound as the light screening film have been generally developed.
Meanwhile, a method of manufacturing a photomask using the blankmask including the hard film is performed by patterning a hard film using a resist film disposed on the hard film as an etching mask, etching a metal film disposed below the hard film using a pattern of the hard film as the etching mask, and removing the pattern of the hard film.
In the method of manufacturing a photomask, however, the processes of patterning the lower metal film using the hard film and removing the hard film have the following problems.
Specifically, in the method of manufacturing a photomask, a washing process using chemicals, for example, Standard Cleaning-1 (SC-1), sulfuric acid (H2SO4), ozone water (O3), and the like is carried out. The washing process has a problem in that a difference in optical density (OD) and critical dimension (CD) uniformity between a central region and an outer region, or a main pattern region and a non-main pattern region occurs as the regions are exposed to a washing material for different times due to a loading effect according to a difference in pattern density between the regions. The difference in optical density and critical dimension on such a photomask affects the critical dimension uniformity of a pattern printed on a wafer due to image contrast enhancement problems during a process of printing a wafer using a photomask.
Also, problems regarding the loading effect occur in a process of removing a pattern of the hard film in the method of manufacturing a photomask. Specifically, after a pattern of a metal film disposed below the hard film using the pattern of the hard film is completely formed, a loading effect in which a time required to remove the hard film is different due to the difference in density between a central region and an outer region, or a main pattern region and a non-main pattern region of the pattern of the hard film occurs during the process of removing the pattern of the hard film. Therefore, a difference in optical density and critical dimension between the regions occurs since a time for which the pattern of the metal film formed below the hard film is exposed to the etching material is different due to the difference in density of the pattern of the metal film. Finally, the difference in optical density and critical dimension on such a photomask results in critical dimension ununiformity at a wafer level and a process margin problem during a process of printing a wafer using a photomask.
The same problems occur in the phase shifting photomask as well as the binary photomask formed using the hard film. Particularly, the problems are increasingly issued as the size of the pattern becomes finer.